LYNN – Police say a robbery and a fight, both involving knives, happened three hours apart from each other on Tuesday.The first occurred at approximately 3:22 p.m., at the Essex Street Market, where a clerk told police he was robbed at knife point by a black male who fled the store with an undisclosed amount of money. The suspect was said to have been wearing a black leather jacket at the time of the incident, including a ski hat and a red ski mask over his face.”A search of the area did not result in any arrests,” Lynn Police Lt. Dave Brown said. “At this time, it would not be prudent to comment on the specifics of the robbery as this incident is currently under investigation with the Criminal Investigation Division.”Then, around 6:10 p.m., Brown said police responded to the area of North Common and Franklin streets on a report of a fight and the person involved had a knife. Upon arrival, the officers found a person fitting the description given and during a pat frisk for weapons, a knife was found.The suspect, Donald Watson, 24, of Revere was also found with drugs and as a result, was arrested and charged with possession of Heroin and Suboxone.Brown said the other person who was involved in the fight did not come forward.Anyone with information about either incident is asked to contact the police at 781-595-2000. Anonymous tips can also be submitted by texting the word tiplynn on a mobile device to tip411 or 847411 or from the department’s Web site at www.lynnpolice.org and clicking the “submit tip” icon.