AUSTIN, Texas (AP) — The seven convicts who escaped from a Texas prison last month systematically overpowered guards and staff over 2« hours and eventually drove unchallenged out the rear exit in a prison vehicle, according to a report released Thursday.

The convicts, who escaped Dec. 13 from the Connally Unit near Kenedy, are charged in the Christmas Eve slaying of an Irving police officer and are still on the loose.

Gary Johnson, director for the institutional division of the Texas Department of Criminal Justice, said inmates were able to take 11 employees and three prisoners hostage in a maintenance storage room, binding them with duct tape and plastic ties and threatening them with homemade weapons.

The report noted at least two security lapses:

— A prison employee noticed several of the unsupervised inmates in the maintenance area but did not report it as suspicious.

— Although several of the hostages managed to free themselves and pull a silent fire alarm, the prison official who called the maintenance area didn't get an answer but did not send anyone to investigate.

"In retrospect, the events fit together like a puzzle. We just didn't fit them together fast enough to keep the offenders from escaping," Johnson said.

Inmates subdued guards and maintenance employees practically one-by-one, binding them with tape, placing pillow cases over their heads and dragging them into a storage room.

A few inmates disguised themselves as maintenance workers to get unchecked access to the prison's entrance and exit area.

Once there, Johnson said, they managed to overpower yet another guard and forced him at gunpoint to open a gate. They drove away in a maintenance vehicle, which they ditched at a nearby Wal-Mart.

The gang stole firearms and left a note saying "You haven't heard the last of us yet."

Johnson acknowledged that a staffing shortage may have indirectly contributed to the problems. The prison guard union has said the prison was 22 staffers short during the shift of the escape.

Johnson called Warden Tim Keith "a good warden" but acknowledged that he may face disciplinary action.

The prison's "snitch system," where inmates inform on each other, also failed. "One of the things that puzzled us the most about this escape is that we did not know anything about it," Johnson said.

Letters left behind by three of the convicts complained of the "tyranny of the Texas prison system" and called for a revolution, The Dallas Morning News reported Thursday.

At least one of the notes reportedly stated, "Freedom's just another word for nothing left to lose," quoting the song "Me and Bobby McGee."