According to a civic leader in Austin, two of the three families targeted by package bombs left on their doorsteps knew each other. The Associated Press reported Tuesday that they were connected through local activism in the black community.

According to the report, it is still unclear how the bombing at a third household is connected.

From the AP: Dixon Mason, a prominent dentist in east Austin, was the grandfather of 19-year-old Draylen Mason, who was killed Monday after carrying a package left at his home into the kitchen and opening it. The elder Mason was friends with Fredie Dixon, stepfather of 39-year-old Anthony House, who died in a similar attack in another part of the city on March 6, said Nelson Linder, president of the Austin chapter of the NAACP.

“I don’t believe in coincidences,” Linder said, explaining that he was concerned by the fact that the families were acquainted.

Still unknown, though, is what connection — if any — the two families had to a third household where another package bomb exploded Monday, injuring a 75-year-old Hispanic woman.

Three package bombs have been left on doorsteps in less than two weeks in Austin, killing two people, wounding two others. Investigators have said the explosions could have been hate crimes since all the victims were black or Hispanic, but they have not ruled out any possible motive.

With a massive manhunt underway to find the killer or killers, Texas police and residents are on high alert and Gov. Greg Abbot has offered a $15K reward for information leading to arrests.