The Attorney General of Sonora state says substitute state congressman Manuel Fernandez Felix hired gunmen to shoot Eduardo Castro Luque on Sept. 14, two days before he was to take office.
Attorney General Carlos Navarro Sugich says the legislator was killed was so that Fernandez Felix could take over the congressional seat.
He said Monday that Fernandez Felix is now considered a fugitive.
Authorities have said another local legislator killed earlier this month on the outskirts of Mexico City was stabbed to death by his wife during a domestic dispute.
Mexican drug cartels frequently target mayors and police officials, but have seldom attacked legislators.
(Copyright 2012 by The Associated Press. All Rights Reserved.)