David Hughes and John Zalsman were charged with obstruction of justice in the 2016 accident that killed 10-year-old Caleb Schwab. The boy was killed as he rode the Verruckt slide at the Schlitterbahn water park in Kansas City. The raft on which Caleb was riding went airborne as it went over a hump and slammed him into a metal pole that supported a net meant to keep riders from flying off the slide. Two women on the raft also were injured.

On Thursday morning, a Federal Court jury in Kansas City, Kansas found the pair not guilty.

Prosecutors had  said Hughes and Zalsman failed to replace a brake mat that fell off the slide two weeks before Caleb was killed, then told investigators that the mat had only been on the slide during testing phases. Video evidence shows the mat was used after the ride opened to customers in 2014, prosecutors said.

“This was not a mistake, this was intentional calculated conduct,” said Adam Zentner, assistant Kansas Attorney General. 

The defense says prosecutors don’t understand how the 17-story Verruckt waterslide functioned. The park’s co-owner and the ride’s designer have also been indicted in Caleb’s death. 

This is the first of the federal trials involving the tragic death.