Oakland officials are investigating why a former police officer is collecting $52,488 a year in medical disability benefits from the city even though he has been working as an FBI agent in Boston.

The unusual case of FBI Special Agent Aaron McFarlane, 41, came to the attention of Oakland officials after the agent was identified last week as the federal officer who shot and killed a key figure last year in the Boston Marathon bombing investigation.

The disability benefit that McFarlane is collecting under the California Public Employees' Retirement System is awarded when a worker is unable to perform the usual duties of his or her current position "due to an illness or injury that is expected to be permanent or of an undetermined duration," said Joe DeAnda, a CalPERS spokesman.

Those on disability retirement are banned from doing similar work for any other government agency in California.

Oakland spokeswoman Karen Boyd said the lifetime payments that McFarlane receives include a 2 percent cost-of-living allowance for each of the past 10 years.

Retired in 2004

"The city of Oakland is investigating the matter and will take further actions as appropriate," Boyd said.

McFarlane retired from the Oakland Police Department on medical disability in 2004, four years after he joined the force as a patrol officer.

He became an Oakland officer the same year that "the Riders" scandal broke, in which four other Oakland officers were accused of beating and planting drugs on suspects in West Oakland