Trained, prepared for the worst and armed to the teeth, federal agents still found themselves outgunned Sunday morning as they raided the compound of a religious cult near Waco, agents said.

As federal agents nursed their wounds and mourned their dead Monday, the tenuous standoff with members of the heavily armed Branch Davidians group continued for a second day.

Bureau of Alcohol, Tobacco and Firearms spokesperson Sharon Wheeler, who said Monday morning that she had had one hour of sleep since the raid Sunday, said the more than 100 ATF agents who raided the sect’s headquarters thought they were prepared.

“There is always that chance in any situation you are in that a firefight could happen,” Wheeler said. “The main problem we had is, I don’t believe we were outmaneuvered or outplanned. The problem we had is that we were outgunned. They had bigger firearms than we had. They were able to shoot through doors, and due to that, a lot of our agents were hurt.”

The battle was the deadliest in the bureau’s history. Four agents were killed, with at least 15 wounded.

The gunfire erupted about 9:45 a.m. Sunday as ATF agents attempted to serve arrest and search warrants on the cult’s leader, Vernon Howell, who legally changed his name to David Koresh, and 75 followers at the sect’s ranch 10 miles east of Waco.

Three helicopters that flew as a diversion for the agents, who charged the fortress-like structure after arriving in cattle trailers, also drew heavy fire.

As the tense standoff continued in a gloomy drizzle, White House officials Monday questioned the timing and execution of the raid, and whether rivalries among federal and local authorities had contributed to the failed effort to arrest Howell.

Law enforcement officials in Washington announced that they had begun an investigation into the deaths.

They expressed concerns that the federal and local authorities may have violated procedures in their approach to the cult’s 77-acre compound.

The officials also said they had reason to believe that some local reporters had been told of the raid, which officials here deny, and that, in general, lax security about the operation may have given the cult the kind of warning it needed to mount the surprise assault that met the agents when they arrived there.

Questioned by reporters Monday about the raid’s execution, Wheeler defended the plan.

“Obviously, they had their reasons for setting it up the way they did,” Wheeler said. “They practiced this in a way where they could get their hands on him (Howell) and protect the people in the compound.”

Some federal officials said Monday that the decision by ATF director Stephen E. Higgins to raid the compound was apparently blown by an informant inside the cult who had been providing federal investigators with allegations that the sect was stockpiling illegal weapons.

According to federal officials, the informant had told ATF investigators that Howell had begun drilling his followers in paramilitary maneuvers using automatic weapons. And the informant also provided enough information about the sect’s compound that ATF agents were able to erect a full-scale replica of the structure and use it in secret rehearsals for the raid over the past two months.

But several federal officials suggested Monday that the informant played both sides of the fence, tipping off sect leaders about the ATF raid.

“Something must have slipped,” one federal official said. “That’s always the chance you run.”

Wheeler said agents will not be sure just kinds of weapons they faced in the deadly siege until after it is over.

“We can’t say absolutely everything they had,” she said. “But we just know from the holes in our vehicles, holes in some of the helicopters and, unfortunately, the wounds of some of our agents, there was some very high-powered ammunition used. They were using some big guns, but I can’t tell you what kind for sure.”

ATF spokesman Les Stanford in Washington said at least one agent was hit by a .50-caliber machine gun.

“The ammunition in a .50-caliber machine gun is the size of your average banana,” Stanford said. “It’s a weapon of war, not a little machine gun Clint Eastwood carries, but the kind on the ground with a tripod that they also use on planes to shoot down other planes.”

The Associated Press, The New York Times and the Los Angeles Times contributed to this story.

Read the Tribune-Herald's 7-part investigative series on the inner workings of the Branch Davidians. Hours after Part Two appeared in print, the ATF raided the group's compound.

Read the Tribune-Herald’s account of the ATF raid on the Branch Davidian compound on Feb. 28, 1993. Four ATF agents and six in the compound were killed in the gunfight.

Read the daily news accounts of the 51-day siege at the Branch Davidian compound near Elk, which began Feb. 28 and lasted until April.

Read the accounts of April 19 and beyond: FBI agents began inserting canisters of tear gas into the Branch Davidian compound in the early morning hours. By noon, it was on fire.