Mohammad Youusef Abdulazeez, the naturalized American-turned Islamic radical who killed four Marines Thursday, was heavily armed, wore an ammo vest and was bent on waging war against America, according to authorities who spoke a day after the horrific attack at two military facilities in Chattanooga.

Abdulazeez, 24, a Kuwaiti-born Chattanooga resident who was killed by police to end his rampage, used an AK-47 to gun down the unarmed Marines after crashing into a gate at the Navy Operations Support Center, according to Rep. Michael McCaul, R-Texas, the chairman of the House Homeland Security Committee. And the troubled gunman, who officials believe had become increasingly radicalized in recent months, wore an ammo vest with multiple rounds of ammunition, while carrying other weapons.

"Based on my experience, I think he was radicalized by these individuals in Syria."

- Rep. Mike McCaul, R-Texas

"Some of the weapons were purchased legally and some may not have been. We will examine that," FBI Special Agent in Charge Ed Reinhold said, speaking at a news conference in Chattanooga hours after McCaul gave his briefing.

In addition to the small arsenal Abdulazeez brought for his maniacal spree, authorities are investigating recent travels by the apparent Islamic radical, including a trip to Jordan in 2014 and another possible jaunt to Yemen.

Sources close to the investigation told Fox News authorities are trying to determine whether Abdulazeez had any contact with extremists during his seven-month stay in Jordan. Abdulazeez is believed to have traveled to the Middle East between April and November 2014.

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Authorities continued to search Abdulazeez's computer Friday, but had not found an extensive online presence and had not uncovered evidence suggesting he was directly inspired by the Islamic State.

The FBI is investigating two blog posts written on Monday to determine if Abdulazeez was behind them, including one that proclaimed that life is "short and bitter" and urged readers to "submit to Allah," the Wall Street Journal reported.  

The National Counterterrorism Center said it is still reviewing its data holdings and watch lists and have so far found no positive hits for Abdulazeez, though it emphasized the review is ongoing.

At approximately 10:50 a.m. Thursday, the gunman opened fire from his silver Mustang convertible at a military recruitment center in a strip mall east of downtown Chattanooga, where one Marine was wounded. Authorities said the shooter then drove 7 miles to a Navy Operations Support Center, crashing his car through a security gate before opening fire on four Marines, killing them. A police officer and sailor were also wounded.

McCaul said Friday he believes Abdulazeez was radicalized online by ISIS members or their supporters in Syria.

"Based on my experience, I think he was radicalized by these individuals in Syria," he said during a press conference at MacDill Air Force Base in Tampa, Fla.

"This is a new generation of terrorists," said McCaul, who was briefed on the case by the FBI. "The threat is real and it comes from the Internet."

"They don't have to travel to Iraq and Syria," he added. "They're already here."

The FBI said Friday afternoon it could not confirm Abdulazeez was inspired by ISIS. Federal authorities also declined to elaborate on the specific weapons used. Reinhold told reporters during a separate news conference that Abdulazeez had "at least two long guns and one hand gun."

"Some of the weapons were purchased legally and some may not have been. We will examine that," Reinhold said.

Abdulazeez got an engineering degree from the University of Tennessee at Chattanooga in 2012 and worked as an intern a few years ago at the Tennessee Valley Authority, the federally owned utility that operates power plants and dams across the South. For the last three months, he had been working at Superior Essex Inc., which designs and makes wire and cable products.

In April, he was arrested on a drunken driving charge, and a mugshot showed him with a bushy beard. In earlier photos, he was clean-shaven.

Hussnain Javid said they graduated a few years apart from Red Bank High School in Chattanooga, where Abdulazeez was on the wrestling team and a popular student.

"He was very outgoing," said Javid, a 21-year-old senior at the University of Tennessee at Chattanooga. "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.

Fox News' Catherine Herridge, Cristina Corbin and The Associated Press contributed to this report.