Shooter identified in deadliest mass shooting in U.S. history

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(CNN) – The FBI investigated Orlando nightclub shooting suspect Omar Mateen for possibly having ties or being a sympathizer to Islamic extremism, according to a law enforcement official and a U.S. official.

There were two cases opened on Mateen in the past, the law enforcement official told CNN. The investigations didn’t find evidence to charge him with anything, the officials said.

Omar Saddiqui Mateen was the gunman who opened fire at a gay nightclub in Orlando, killing at least 50 people, two law enforcement officials told CNN.

The 29-year-old suspect was known to the FBI, the officials said – one of hundreds of people on the agency’s radar suspected of being ISIS sympathizers, according to two law enforcement officials.

There was no indication he was plotting to carry out an attack, the officials said. Investigators haven’t found evidence yet to show that the attack was tied to ISIS, according to the officials.

Mateen, who was killed by police, is from Fort Pierce, Florida, the officials said.

A law enforcement source told CNN that Mateen worked as a private security guard. He rented a car and drove to Orlando to carry out the attack, the source said.

FBI teams and local law enforcement are working to clear Mateen’s apartment, a federal law enforcement source said.

Agents are going through the apartment with bomb squads and investigating the materials there, the source said.