James Sikking, who starred as a hardened police lieutenant on "Hill Street Blues" and as the titular character's kindhearted dad on "Doogie Howser, M.D.," has died at 90.

Sikking died of complications from dementia, his publicist Cynthia Snyder said in a statement Sunday evening. Born the youngest of five children on March 5, 1934 in Los Angeles, his early acting ventures included an uncredited part in Roger Corman's "Five Guns West" and a bit role in an episode of "Perry Mason." He also secured guest spots in a litany of popular 1970s television series, from the action-packed "Mission: Impossible," "M.

A.S.H.

" "The F.B.I.

," "The Rockford Files," "Hawaii Five-O" and "Charlie's Angels" to "Eight is Enough" and "Little House on the Prairie." "Hill Street Blues" would debut in 1981, a fresh take on the traditional police procedural. Sikking played Lt.

Howard Hunter, a clean-cut Vietnam War veteran who headed the Emergency Action Team of the Metropolitan Police Department in a never-named city. The acclaimed show was a drama, but Sikking's character's uptight nature and quirks were often used to comic effect. Sikking based his performance on a drill instructor he'd had at basic training when military service cut through his time at the University of California, Los Angeles, from which he graduated in 1959.

"The drill instructor looked like he had steel for hair and his uniform had so much starch in it, you knew it would sit in the corner when he took it off in the barracks," he to.