Knock Knock, Who’s There?At 4:11am this morning officers in District 3 responded to 25 Calder Street in Dorchester for a man with a gun. They spoke with a victim who stated that an unknown male came knocking on his door demanding he open it. The victim looked through a peephole and observed the suspect, whom he did not know, display a firearm and demand the door be opened. The victim did not comply and called 911. A search of the area was made to no avail. This incident remains under investigation. East Boston Man Trips and Gets Robbed At 1:30am this morning, officers from District 7 were sent to Mass General Hospital to meet the victim of a robbery. According to the victim he was walking along Meridian Street and was approached by two males. One of the males showed a gun and demanded money from the victim. The victim began to run away and tripped injuring his right eye in the process. One of the suspects then confronted the victim as he lay on the ground and took his money and cell phone. Both suspects remain at large. Drugs, Gun Recovered in Roslindale Apartment Members of the Special Investigations Unit along with the youth Violence Strike Force executed a search warrant at 20 Brookway Terrace at 1:12am this morning. During the search officers recovered a significant amount of crack cocaine packaged for sale and a significant amount of marijuana. Also recovered was a Taurus 9mm handgun and ammunition. Arrested in connection with the search warrant was: Marvin Antoine, 20 of Stoughton, Jonathan Santiago, 17, Pedro Colon, 19, and Julio Cruz, 54 all of Roslindale. Firearm Found in Dorchester Yard Officers from District 11 found a loaded 380-caliber gun in the rear yard of 20 Melbourne Street at about 12:05am this morning. Officers had responded to a call for a man with a gun at that location earlier to no avail. The gun was made safe and turned over to the ballistics unit for testing. Charlestown Minor Absolutely Under Arrest Officers assigned to the Tactical Bike unit observed a large group of males in the area of 85 Dunstable Street. The officers approached to disperse the group and noticed a young man unsteady on his feet holding a bottle of vodka. The officers determined that the young man was drunk and not yet of legal age to possess alcohol. After admitting to the officers that he had a couple of drinks, he was arrested for being a minor in possession of alcohol.