A masked gang of heavily armed robbers stormed into a Northwest Washington bank yesterday morning, firing two shots into the ceiling and escaping with a bundle of cash in what police said was the sixth holdup by the group this year.

Wearing heavy clothing and carrying assault-style rifles, the men acted with precision in carrying out the robbery of the SunTrust Bank branch in the 5000 block of Connecticut Avenue NW, a busy strip of stores and restaurants. Police said at least two robbers entered the bank about 10:50 a.m. while an accomplice waited outside with a getaway vehicle.

The men escaped with about $50,000, according to a law enforcement official. The gang has netted about $370,000 in the six robberies, officials said. No one has been seriously hurt in any of the robberies, but the gunmen have fired weapons in three of them, heightening police concerns.

"I hope we can hurry up and get them before they kill somebody," said D.C. Police Chief Charles H. Ramsey. "This is a very vicious crew."

The robbers' escape was captured in chilling detail on a tape recorded by a television news crew that was on another assignment in the neighborhood. WTTG-TV (Channel 5) showed video of a masked man carrying an assault rifle crouching outside a minivan parked alongside the bank. A few seconds later, two other men -- also masked and carrying assault rifles -- are seen running out of the bank. One stumbled but recovered before falling to the ground.

All three men got into the Dodge Caravan, which sped across Connecticut Avenue and screeched down a side street. The minivan was found burning a short time later in the 2500 block of Northampton Street NW, a residential area less than two miles from the bank. The robbers got away.

Ammunition left in the van began exploding in the blaze, and the fire created a huge cloud of black smoke. Firefighters raced to that scene as more and more police converged on the bank.

The robbery fits the pattern of the other crimes, police said. All six robberies took place between 10 a.m. and noon and were carried out by masked, well-armed men using stolen vans. The Caravan used yesterday had been stolen earlier in the morning in Prince George's County. After the crimes, the vans typically have been found abandoned or burned in an apparent effort to get rid of evidence.

Capt. Willie Smith of the 2nd Police District said two officers were at a traffic stop within blocks of yesterday's robbery. By the time they had raced to the bank after hearing a report of the robbery over their police radios, the gunmen were gone.

"It was just a matter of minutes," Smith said, adding that the bank's patrons were "really shaken up" by the ordeal.

Witnesses described an operation that was executed with military precision. People who live and work near the busy street said they were shocked by the brazen nature of the crime.

"They're bold," said Carrie Singer, who lives near the bank. "Connecticut Avenue at 11 o'clock in the morning?"

Scott McCathran, the WTTG photographer who taped the escape, said he was preparing to shoot a promotional video at a nearby fire station when a man screamed that two armed men had entered the bank.

McCathran said he immediately ran toward the bank, adding, "I wasn't thinking at the time."

He hid behind a car just across the street from the bank, he said, and began filming. He zoomed in on the van as the gunmen drove off. "Maybe some of the tape can help catch the guys," he said.

In the Chevy Chase neighborhood where the minivan was set ablaze, residents also were taken aback by the drama.

Anna DeFina, a Georgetown University professor, was at her computer when she heard a loud explosion. "I saw flames coming up. It was furious," she said.

David Keil, who has lived in the neighborhood for 45 years, said he and his wife thought they were hearing firecrackers. Keil said he first saw flames coming from the passenger side of the vehicle, which quickly became engulfed in flames.

The FBI is offering a $50,000 reward for information that helps lead to the assailants. People with information are asked to call the FBI at 202-278-2000 or D.C. police at 202-727-9099. Prince George's County police also are investigating.

The first robbery occurred Jan. 22, when five masked and armed men stormed into a Bank of America branch at 5911 Blair Rd. NW, taking $140,000. The robbers' take in the other robberies has diminished considerably. Yesterday's haul could present problems: Authorities said it was rigged with a red dye meant to permanently stain it.

Three robberies have been in Northwest Washington. The others took place in Northeast Washington, Temple Hills and Hyattsville. Shots were fired in a robbery June 12 at a Northeast Washington bank and in a May 10 robbery in Temple Hills. In the latter case, authorities said, two gunshots hit a Prince George's police car.

Staff writers Nicole Fuller and Allan Lengel contributed to this report.

A robber crouches outside the SunTrust bank during the holdup. "I hope we can hurry up and get them before they kill somebody," said D.C. Police Chief Charles H. Ramsey. FBI agents examine a minivan stolen yesterday morning, used in the bank robbery on Connecticut Avenue NW and then burned nearby.