PORTLAND, Ore. (AP) _ A man with an assault rifle shot two men in the parking garage of a Portland building Thursday, then holed up in an office with at least four hostages, police said. Two hostages were later released.

The unidentified gunman, wearing fatigues and a black beret, was still holding at least two female hostages four hours after the standoff began. No motive was immediately known.

``He can't go anywhere,'' police Lt. C.W. Jensen said. ``We've got everything secured right now. We've got officers all over the building.''

Witnesses said the man, who appeared to be in his mid-30s, left the garage after the shooting and entered the lobby of the 30-story KOIN Tower.

There, witnesses said, he began firing at officers, who were responding to building alarms, seized a hostage and barged into the Charles Schwab brokerage, where he took more hostages.

One hostage, identified as stockbroker Ken Aiken, was released about two hours after the standoff began. A woman was released after another 1 1/2 hours.

Police were negotiating with the gunman, who they believe still had at least two women hostages.

The wounded men were identified as Alan Kolkemo, 24, of Beaverton, who was shot twice in the back, and Howard Barley, 45, of Milwaukie, who was shot three or four times in the leg. Both were in fair condition at University Hospital.

One Charles Schwab employee, Kori Allen, 34, was treated for a head injury that she suffered while trying to get out of the building.

According to one witness, the man began ordering people into the Charles Schwab office after the gunfire triggered the building's alarms and shut down the elevators.

At one point, he threw down his rifle and pulled a handgun from a bag, said the KOIN-TV employee who spoke on condition of anonymity. The station has its offices in the basement of the building.

``I didn't take him seriously. He seemed real fidgety. He didn't seem to have control,'' said the woman, who was able to escape through a back exit.

Nick Mayer, who works for AT&T Capital, another tenant in the building, said he saw the gunman grab a woman from behind and heard shots as he ran out of the building.

``I came down the stairs and saw a guy with fatigue pants and a rifle with a scope on it. I heard shots. He was shouting, `Come here,' at me,'' Mayer said.

Soon after the shooting, police closed off streets around the tower, which is one block from the Willamette River waterfront. Its tenants include several major law firms. It also houses a six-screen movie theater and 11 floors of condominium units.