By George P. Hassett

Police took two convicted drug users by surprise Saturday morning as they prepared to shoot heroin in the parking lot of the Gulf Gas Station on Alewife Brook Parkway.

Robert White, 28, of 341 Alewife Brook Parkway and Walter Hussey, 29, of 11 Riverside Ave., Danvers, jumped in their seats when Officer Richard C. Lavey opened their car door without warning, police said.

Lavey was responding to a report of two men "shooting up drugs," when he approached the car, police said. White and Hussey were too fixated on the cooking of the heroin to notice Lavey approach, police said.

When lavey opened the door, White allegedly dumped the contents of the spoon onto his car's center console.

Police allegedly found three syringes, drug paraphernalia and an orange pill in the car. Police said Hussey has a 2003 conviction for trafficking a class B drug and White a 2005 conviction for possession of a class A drug.

White and Hussey were each arrested and charged with possession of a class A drug, subsequent offense, after officers responded to a report of two men "shooting up drugs," police said.

Somerville police officer Richard Lavey pulled up next to Hussey's car.