Warner had not previously been on law enforcement's radar, according to Tennessee Bureau of Investigation Director David Rausch.
He was arrested on a
charge of marijuana possession for resale in 1978, when he was 21, but otherwise had no criminal history.
Investigators from the TBI are working with the FBI, ATF and Nashville police on interviewing other family members as well as Warner's neighbors. They are talking to anyone who knew Warner and trying to get his history as best they can, authorities said.
Before exploding, the RV was parked right outside an AT&T transmission building, which sustained significant damage in the blast, knocking out wireless service for much of the region, authorities said.
Warner's father previously worked at AT&T, according to Rausch, and he said investigators are looking into whether that may be relevant to the motive.
What we know about the 63-year-old Nashville bomber
The AT&T building was the central office of a telephone exchange, with network equipment in it, the company said. Some internet access in Tennessee and surrounding states
went down after the blast, as well as some cellphone and 911 service in counties in Tennessee and Kentucky.
The Federal Aviation Administration temporarily halted flights out of Nashville International Airport Friday due to telecommunications issues.
Petula Clark shocked and confused after 'Downtown' was used in Nashville bombing
The song begins like this:
When you're alone and life is making you lonely
You can always go downtown
When you've got worries, all the noise and the hurry
Seems to help, I know, downtown'