The Indianapolis mass shooting suspect was known to federal and local authorities prior to the attack. A family member of the alleged shooter has reached out to authorities to warn of the suspect’s potential for violence, according to three law enforcement sources who have been briefed on the matter.

It was not clear when the warning was given, but public relations and the FBI were tracking the publicity, which opened a preliminary investigation of a possible threat.

The FBI eventually finalized its investigation after concluding that there wasn’t enough evidence to continue it, according to sources, which failed to state why federal investigators had dropped the matter.

The suspect has not been publicly identified. The FBI is helping the Indianapolis subway police “to find the suspect at home,” said FBI special agent Paul Keenan at a press conference on Friday morning.

When asked if the authorities had any evidence that this attack was going to take place, the police said no.

“We’re still working with FedEx Security on anything that might indicate this is about to happen,” said Craig McCartt, assistant chief of police for Indianapolis, on the same Friday.

A police spokesman declined to comment on CNN’s coverage.

“As soon as we have clearly identified who he is, we can research further,” said spokesman Genae Cook.