ATLANTA (AP) — Two Georgia prison guards failed to properly search and secure their prisoners on a transfer bus, enabling two inmates to free themselves and rush forward to overpower and kill the guards who had violated numerous security procedures, officials said Friday in reports on the deadly June escape.

The two reports lay the blame for the escape on the slain guards, and corrections officials said numerous procedures are being revised in response.

"My heart remains heavy with the realization of the gravity of these losses to the families, to our agency and to our state," Georgia Department of Corrections Commissioner Greg Dozier told reporters before detailing the report findings and plans for sweeping changes.

"I am determined not to allow an event like this to take place again," Dozier said.

The security lapses enabled inmates Ricky Dubose and Donnie Rowe to exit the inmate compartment, overpower Sgt. Christopher Monica and Sgt. Curtis Billue and use the officers' guns to kill them, according to a report from an external review conducted after the June 13 escape.

The external review conducted by representatives from several state law enforcement agencies focused on the escape. An internal review by the Department of Corrections was meant to evaluate agency security procedures for inmate transport.

Dubose and Rowe carjacked a driver and sped off, sparking an intense manhunt that culminated two days later in Tennessee. The two are accused of killing Monica and Billue and face charges including murder.

The external review report says it began when Monica and Billue missed what's believed to be a toothbrush when searching Rowe before he boarded the bus around 4:42 a.m. The officers failed to double-lock the inmates' restraints, which is required by policy. That allowed Dubose to remove his handcuffs within two minutes of boarding the bus and then to remove the cuffs from Rowe and many other inmates, the report says.

The "single greatest point of failure" was the failure to secure the gate between the inmate compartment and the officer compartment on the bus, the report says.

The officers violated policy by leaving their assigned handguns in storage boxes throughout the trip rather than wearing them, and by not wearing ballistic vests. Billue's vest was later found in his personal vehicle. Monica didn't even have a ballistic vest, and a separate vest that blocks stab wounds was retrieved from his family.

The bus also left Baldwin State Prison before sunrise, despite a policy that says prisoners shouldn't be transported in the dark unless there's an emergency and pre-dawn transport is approved by the warden.

When the bus arrived at Hancock State Prison at 5:43 a.m. to pick up additional inmates, both officers exited the bus, leaving the inmates unattended. An inmate can be heard on video telling the other inmates that the lock on the gate between the compartments wasn't locked. It took Rowe about a minute to get the door open using the implement he'd smuggled aboard, the report says.

Rowe and Dubose went into the officers' compartment and rifled through the officers' lunches, returning to the inmate compartment before the guards returned with more inmates at 6:05 a.m. and again failed to lock the gate, the report says.

Dubose removed his uniform shirt about 20 minutes later and he and Rowe began moving toward the front of the bus a short time later. As Rowe began attempting to reopen the security gate, video shows most of the other inmates moving toward the back of the bus, the report says.

Rowe and Dubose got through the gate at about 6:40 a.m., attacked and killed the guards with their own guns within seconds and then carjacked the passing driver, the report says.

Several inmates who were on the bus said Monica was asleep during portions of the trip, but that could not be confirmed by video, the report says.

Dozier said three changes were made immediate following the escape: a trail vehicle was added for every prison transport by June 20; all transportation officers underwent refresher training between June 20 and June 28; and a duty officer was assigned at all facilities to ensure compliance with transport procedures.

Going forward, even more changes will be implemented, he said. They include:

— Key-retaining padlocks on the doors to the inmate compartment on transfer buses to ensure the key couldn't come out of the lock without the lock being secure;

— Implementation of a pre-departure checklist before inmate transport;

— Continuing use of newly implemented trail vehicles for all inmate transports;

— Video surveillance throughout the bus, not just in inmate compartment;

— Annual refresher training for transport officers;

— Updating post orders defining duties for officers;

— Extensive annual audit focusing solely on inmate transport.