They obliterated their own bomb truck in a "controlled" explosion.
The massive explosion that rocked LA and wounded 17 people was likely caused by an "apparent miscalculation" by the bomb squad, authorities have admitted.
Dozens of homes, businesses and vehicles were badly damaged late last month when LAPD attempted to carry out a "controlled" explosion on a cache of illegal fireworks it had seized — but the explosion was anything but controlled.
Video from the scene show the truck brought in to contain the detonation instead being obliterated — and LAPD Chief Michel Moore believes the embarrassing slip up was caused by "human error".
The incident occurred on June 30, when a tip off led police to a huge 5,000lb stash of fireworks stockpiled at a home on East 27th Street.
While most were safely packed up and confiscated, officers determined that some of the fireworks were leaking, and were too unstable to move. Thus the decision was made to bring in the 'total containment vehicle': a truck bearing a specifically designed iron chamber, inside which controlled explosions can be carried out.
The vessel is designed to withstand a maximum capacity of 25lbs of explosives. But according to Moore, the officers eyeballed the weight of the fireworks rather than using a scale.
They believed they were putting in 16.5lbs of explosives. Forensics later determined the payload was closer to 42lbs — almost twice the amount the vessel was built to handle.
Video from the scene show the massive explosion obliterating the truck, overturning nearby cars and sending shrapnel everywhere.
"Based on information gathered at this point, it is believed that the net explosive weight placed into the [vessel] exceeded its rated capacity," Moore said at a news conference, per KTLA5.
He said bomb squad specialists had sliced open two of the fireworks to extract a sample and had estimated the weight instead of using a scale — as visual and physical estimations are permitted under LPD protocol.
The LAPD supervisor and bomb technicians involved have all been removed from the field as the investigation continues, Moore said.
He also said the destroyed containment vessel is being examined to see if any of its had components failed; however the truck had been in service for more than a decade beforehand, and had previously carried out 41 controlled explosions without issue.
"If mistakes are made in regards to established protocols, I'll hold the appropriate individuals accountable," chief Moore said.
"I want to personally express my apologies to every resident, business operator and customer that was dramatically impacted by this incident … I acknowledge that there are many more individuals who were traumatized by the explosion itself," he added.
LAPD had evacuated homes as a precaution before the detonation; nevertheless six residents were still wounded in the explosion.
"This is by far one of the LAPD's largest blunders in recent history, which has further betrayed the trust of our South LA community," LA City Councilman Curren Price said in a statement.
"My constituents feel that this was a blatant disregard for their safety and our community of color. This tragedy could have been prevented and I wholeheartedly believe that additional safety precautions would have been taken in a more affluent community."