A contingent of St. Louis-area police union members have been providing personal protection for former Ferguson officer Darren Wilson, an unusual security arrangement that will likely continue indefinitely despite the officer's recent resignation from the force, a top union official said Monday.

Darren Wilson officially resigned from the Ferguson Police Department on Saturday night. The announcement comes nearly 4 months since he shot and killed Michael Brown and less than a week since a grand jury decided not to indict him.

Jim Pasco, executive director of the national Fraternal Order of Police, told USA Today local FOP members have been voluntarily providing Wilson's security that has included their involvement in shuttling the officer among undisclosed locations since his involvement in the Aug. 9 fatal shooting of teenager Michael Brown.

"I don't know how he can live a normal life,'' Pasco said, adding that his "days as a cop are over.''