A day after Bellevue police announced there had been three armed robberies downtown within 10 days, plainclothes officers caught a convicted sex offender Tuesday night buying beer for four teenagers.

Officer Michael Chiu said the officers usually patrol areas such as car lots, but had been temporarily reassigned to downtown because of the three robberies.

Chiu said the arrest was probably not connected to the robberies, but was a result of the increased police presence in the area.

Two plainclothes officers said they saw 29-year-old Carey James Toomy and four teenagers approach a convenience store on Main Street around 8 p.m. and watched Toomy come out with four 20-ounce cans of Budweiser and begin to give them to the youths.

The name Toomy initially gave officers turned out to be fake. A fingerprint check revealed his identity and showed that he had been convicted of two sex crimes and had an outstanding warrant from the California Department of Corrections for failing to register as a sex offender.

Chiu said Toomy's sex convictions were in California and included a lewd act with a child and sexual assault. Toomy had recently been released from California's San Quentin prison and moved to Kirkland.

When officers searched Toomy's backpack, Chiu said, they found beer and a pornographic magazine featuring male teenagers. Chiu said this arrest probably would be a parole violation for Toomy, who also has convictions for assault, theft, possession of stolen property and auto theft.

Toomy is in King County Jail awaiting extradition to California. The four teens — from Bellevue, Kirkland and Snohomish — were released shortly after the incident and were not charged. Chiu said that because the teenagers hadn't consumed any alcohol, they had not committed a crime.

Bellevue police are still looking for the suspects who committed the three robberies. The incidents include:

• Aug. 12, around 9 p.m., three teenagers demanded a wallet from a 17-year-old sitting outside the Ground Zero teen center at 100th Avenue Northeast. Police say the suspects had a folding knife and implied that they had a gun. They took $2 in cash and cigarettes.

• Aug. 17, around 10 p.m., three 16-year-old girls were assaulted when two young men ran toward them near the downtown park, pulled a knife and threatened them. The men stole two purses, two cellphones and less than $100 in cash.

• Monday, around 8 p.m., a 26-year-old homeless man was approached by three men near the corner of Northeast First Street and 102nd Avenue Northeast. One of the suspects pulled out a handgun and stole the homeless man's wallet with $20 in it.

Ari Bloomekatz: 206-464-2540 or abloomekatz@seattletimes.com