Surveillance video shows moment bomb explodes in Austin

AUSTIN, Texas – Home surveillance video obtained by KPRC captured the moment a bomb exploded Sunday night in 4800 block of Dawn Song Drive in Austin.

Richard Herrington heard the 8:32 p.m. explosion from his home in the Travis County neighborhood.

WATCH: Surveillance video captures moment bomb went off in Austin

“I would describe it as a thump. A loud thump,” Herrington said.

Herrington said he instantly recognized the sound.

“I was in the Army and went through Army training,” he said. “That’s how I knew it was a bomb when I first heard it.”

The bomb injured two men -- 22 and 23 years of age -- as they were walking along the sidewalk.

Austin Police Chief Brian Manley said the men accidentally set of a tripwire attached to a bomb.

Herrington took his two granddaughters to play at a park nearby the explosion site just hour before it happened. A day after the bombing, he said he couldn’t help but think what if.

“My first thought was my granddaughter could have run ahead of us and tripped that tripwire,” he said. “It’s terrifying.”

Sunday’s bombing marks the fourth in Austin since March 2.

In the prior three incidents, a package with an explosive device was left on the doorstep of victims.

Anthony Stephan House, 39, and 17-year-old Draylen Willam Mason were killed handling the packages.

Mason’s mother and a 75-year-old woman were injured by the explosions.