WALNUT CREEK (CBS SF) — A man was critically injured following what police call an attempted murder at a park in Walnut Creek Monday, and police were looking for a suspect.

Walnut Creek police said dispatchers received a 911 call at 5:36 a.m. from someone reporting a man appeared to be injured at the gazebo in Civic Park.

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Officers arrived to find a man unconscious with a serious head injury, police said. Medics took the unidentified victim to a hospital where he was listed in critical condition.

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Investigators determined the victim was with a man earlier in the morning and that person is believed to the suspect in the assault. He was described as a White man in his 40s, about five-foot-one to five-foot-three with thin gray hair, clean-shaven, and missing several teeth.

Police said based on the preliminary investigation it believed the incident was isolated and there was not any active threat to the community.

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Anyone with information about the incident was asked to call Walnut Creek Police Detective Gerstner at 925-256-3578.