AUSTIN – Investigators are still looking for the person behind three package explosions that killed two people and hurt two others in Austin.

ATF sent 30 agents including certified explosive specialists. They are fragments left outside homes where packages exploded. Authorities are shipping each piece to ATF’s lab in California where agents are reconstructing each explosive hoping to learn what was in each package, how it worked and perhaps who built it.

In east Austin, where 17-year-old Draylen Mason died, two sets of FBI agents knocked on Lee Ferguson’s door.

“They wanted to know if I heard anything, if I had security cameras (and) had I seen anybody strange in the neighborhood lately,” he said.

All four victims hurt in the last two weeks are minorities, Austin Police Chief Brian Manley said. However, authorities do not know why each was targeted.

The FBI sent forensic profilers to help find potential suspects.

All of it came as Travis County 911 received 265 calls from people wary of unexpected or unmarked packages. So far, none of them are connected to this investigation, Chief Manley said.

“We are not going to leave any stone unturned and we’re going to follow up on every lead until we can clear this case,” he added.

Crime Stoppers offered $65,000 reward for information leading to an arrest.