A warrantless arrest requires probable cause which is defined as under the totality of circumstance known to the arresting officers, a prudent person would have concluded that there was a fair probabilty that the subject had committed the crime. It is an objective standard. If probable cause has dissipated after the arrest, the subject must be released. Here, the police had been shot at by a hispanic male who fled in a car that the police were able to describe with specificity. Several hours later, the police located the car and observed Lopez drive up and drop off a female who entered the car and left, followed by Lopez. Although the police had sufficient grounds to initially detain Lopez as the suspected shooter, probable cause to believe that he was the shooter had dissipated by the time he was brought to the police station. But because probable cause is an objective standard, the arrest continued to be valid because even though the police subjectively believed Lopez was responsible for the shooting, probable cause existed to believe that he was an accessory to the shooting. Accordingly, the search subject to the arrest was valid.