When Harry R. Green Jr. showed up for orientation for a job as a security guard on Wednesday at 1776 F St. NW, he politely introduced himself to a guard and said little else.

The guard was surprised to see Green dressed in full D.C. police regalia, complete with a name tag, badge, handcuffs, police radio and even a bulletproof vest.

But it was the 9mm Glock semiautomatic handgun Green carried that unnerved the guard and prompted him to telephone a supervisor, who called D.C. police.

"Something didn't look right," said David Marvil, president of Securiguard Inc., a McClean-based security company that had recently hired Green. "His credentials didn't jibe."

Green, a 28-year-old Prince George's County resident was charged with impersonating a police officer and carrying a pistol without a license and unregistered ammunition.

Now, details are emerging about the man who is charged with committing a crime that D.C. Police Chief Charles H. Ramsey and Green's former employers characterized as bizarre and baffling.

"The situation is absolutely insane," said James Holloway, a former D.C. police officer and executive director of Unlimited Security, a company that once employed Green. "How he could pull this off on the police department is sick."

People familiar with Green describe him as quick-tempered. While working as a security guard for Unlimited Security in 1996, he allegedly got into a fight with another man while assigned to the D.C. wharf.

Green's father, Harry Sr., happened to be nearby and rushed to his son's aid and allegedly hit the man repeatedly with a blackjack, according to sources and court records.

Harry Sr., is a retired correctional officer for the D.C. Department of Corrections. He was hired in 1972 and worked until 1975 at the Lorton Correctional Complex in Fairfax County. He went out on paid disability until 1986, when he retired, sources said.

The man sued the Greens, and the case is pending in D.C. Superior Court, according to records. The younger Green was terminated several weeks after the incident, Holloway said.

"We terminated Harry because he didn't show up for work," Holloway said. "He was just a bad employee in general."

Green then got a job working for Colorado Security in Northwest Washington and was hired recently by Securiguard. But for the last several months, and perhaps as long as two years, Green, who is 5 feet 7 inches tall and weighs 230 pounds, posed as a D.C. police officer, working side by side with officers, possibly attending roll calls and possibly making at least two arrests in July, police officials said yesterday. Police administrators are reviewing police reports to determine whether Green was the arresting officer on any cases. Green has given officials a handwriting sample, Ramsey said.

He obtained a department-issued police radio and bought a name tag from a police supply store, officials said.

It is unclear how he got the badge, bulletproof vest and uniform.

Green purchased the gun from Realco Guns Inc., a gun dealer in Prince George's County. He applied for a license on Jan. 29 and it was approved by the Maryland State Police on March 1, according to Realco owner Greg DelReal.

"Because he was in full uniform and carried all the police equipment, the people who dealt with him thought he was a legitimate police officer," said D.C. Assistant Police Chief Brian Jordan, whose major crimes unit is investigating the incident.

Although Green dressed as an officer and rode along with them on calls, there's "nothing to indicate" he ever applied to the police academy, Jordan said. While posing as an officer, Green seemed to follow department rules, Jordan said.

"We are still trying to figure out everything there is to know about this guy," Ramsey said yesterday. "He's been cooperative. I guess he just wanted to be a police officer."