Chilling Quote From Chattanooga Gunman's Past

The man who authorities say killed four Marines in an attack on a military recruiting center and another U.S. military site was a 24-year-old, Kuwait-born engineer who had not been on the radar of federal authorities until the bloodshed.

Beyond that, little is known about Muhammad Youssef Abdulazeez of Hixson, Tennessee, or what motivated his rampage. Federal authorities were looking into the possibility it was an act of terrorism, but there is no evidence yet that anyone else was involved - or that the public is in any danger.

Officials have said they do not know why the shooter targeted the facilities and have not said what weapons he used.

CBS Boston says one of the Marines killed was Gunnery Sgt. Thomas Sullivan, 40, a native of Springfield, Massachusetts. The station cites the India Battery 3rd Battalion 12th Marines Facebook page.

According to MassLive.com in Springfield, Sullivan served two tours of duty in Iraq, and earned a Purple Heart, CBS Boston adds.

In addition, a bar run by Sullivan's brother posted a tribute.

People gathered at a local church Thursday night to pray for the shooting victims, reports CBS News correspondent Dean Reynolds.

Even the exact spelling of the gunman's first name was not clear: Federal authorities and records gave at least four variations. Residents in the neighborhood where Abdulazeez is believed to have lived said they didn't know him or his family well.

Hussnain Javid, a 21-year-old senior at the University of Tennessee at Chattanooga, said Abdulazeez studied electrical engineering at the same college. They both graduated from Red Bank High School in Chattanooga several years apart. Javid said Abdulazeez was on the high school's wrestling team and was a popular student.

Abdulazeez was not on any U.S. terror list and the FBI said no connections have been found to the Islamic State of Iraq and Syria (ISID) or Muslim extremists.

A U.S. official told The Associated Press there was no indication Abdulazeez was on the radar of federal law enforcement before the shootings. The official was not authorized to discuss the case and spoke on condition of anonymity.

CBS News correspondent Jericka Duncan reports Abdulazeez's high school yearbook shows his senior photo, with the quote, "My name causes national security alerts. What does yours do?"

Officials confirmed to CBS News that his father was under investigation several years ago over possible ties to a foreign terrorist organization.

FBI agent Ed Reinhold said Abdulazeez had "numerous weapons" but would not give details. He said investigators have "no idea" what motivated the shooter, but "we are looking at every possible avenue, whether it was terrorism, whether it's domestic, international, or whether it was a simple criminal act."

Reinhold also told a news conference late Thursday that "there is no indication at this point that anybody else was involved."

"Obviously, we're still at the beginning of this investigation," he said. "We will explore any possibility and that includes whether or not anyone else was involved."

U.S. Attorney Bill Killian told the news conference that "as far as we know at this juncture, there are no safety concerns for the general public."

The U.S. National Counterterrorism Center said it has seen nothing so far to connect Abdulazeez to any terrorist organization, but intelligence officials are monitoring the investigation closely. The Islamic State group has been encouraging extremists to carry out attacks in the U.S., and several such homegrown acts or plots have unfolded in recent months.

Authorities would not say publicly how the gunman died, but a U.S. official said investigators believe Chattanooga police fired the shot that killed him. At least one military commander at the scene also fired at the gunman with his personal weapon, but forensic investigators determined that police killed him, the official said. An autopsy will determine whose shot ended his life, authorities added.

Kevin Emily, Abdulazeez's high school wrestling coach, thought of himself as a father figure to the teens on his team. He told Duncan he spent much of Thursday fielding phone calls from former students who heard the news.

"I was numb when I heard it because I heard it from one of my wrestler's parents," Emily said. " ... They're just like, 'Coach, can you believe it? Can you believe Muhammad did that?"'

"I don't have any bad words to say about him as an individual that wrestled for me and neither do they. So we're all in shock and we're all hurt."

The Tennessee Valley Authority confirmed Abdulazeez had been an intern at the public utility a few years ago.

"He was very outgoing," Javid said. "Everyone knew of him."

Javid said he occasionally saw Abdulazeez at the Islamic Society of Greater Chattanooga, but the last time was roughly a year ago.

The shootings took place minutes apart, with the gunman stopping his car and spraying dozens of bullets first at a recruiting center for all branches of the military, then driving to a Navy-Marine training center 7 miles away, authorities and witnesses said. The attacks were over within a half-hour.

In addition to the Marines killed, three people were reported wounded, including a sailor who was seriously hurt.

"Lives have been lost from some faithful people who have been serving our country, and I think I join all Tennesseans in being both sickened and saddened by this," Tennessee Gov. Bill Haslam said.

Within hours of the bloodshed, law officers with guns drawn swarmed what was believed to be Abdulazeez's house and two females were led away in handcuffs.

A dozen law enforcement vehicles, including a bomb-squad truck and an open-sided Army green truck carrying armed men, rolled into the Hixson neighborhood, and police closed off streets and turned away people trying to reach their homes.

The names of the other victims were not immediately released. In addition to the wounded sailor, a Marine was hit in the leg but not seriously hurt, and a police officer was shot in the ankle, authorities said.

In Washington, President Obama pledged a prompt and thorough investigation and said the White House had been in touch with the Pentagon to make sure military installations are being vigilant.

"It is a heartbreaking circumstance for these individuals who served our country with great valor to be killed in this fashion," Obama said.

Vice President Joe Biden likewise said: "Their families have already given a lot to the country, and now this."

The shootings began at the recruiting center on Old Lee Highway, where a shot rang out around 10:30 or 10:45 a.m., followed a few seconds later by more fire, said Sgt. 1st Class Robert Dodge, leader of Army recruiting at the center.

He and his comrades dropped to the ground and barricaded themselves in a safe place. Dodge estimated there were 30 to 50 shots fired. Doors and glass were damaged at the neighboring Air Force, Navy and Marine offices, he said.

The recruiting center sits in a short strip mall, between a cellphone business and an Italian restaurant, with no apparent special security. The shooter fired at the center from inside his car, but then got out of the vehicle to shoot the four marines at the Navy Operational Support Center and Marine Corps Reserve Center Chattanooga, Reinhold told a news conference late Thursday.

The Navy-Marine center, situated in an industrial area of the city, is a fenced-off installation. Its two entrances have unmanned gates and concrete barriers that require approaching cars to slow down to drive around them.

Marilyn Hutcheson, who works at Binswanger Glass across the street, said she heard a barrage of gunfire around 11 a.m.

"I couldn't even begin to tell you how many," she said. "It was rapid-fire, like pow-pow-pow-pow-pow, so quickly. The next thing I knew, there were police cars coming from every direction."

She ran inside, and she and other employees and a customer waited it out with the doors locked. The gunfire continued with occasional bursts for what she estimated was 20 minutes. Bomb squads, SWAT teams and other local, state and federal authorities rushed to the scene.

"If it was a grievance or terroristic related, we just don't know," she said.