Bully son

[BRYANDCAMSMOMMY]

ok so i have been meaning to ask this question for awhile. i currently have an almost 3 yr old and a 10 month old.  My 10 month old just started crawling on mothers day. Dh has been gone since Febuary. Ds 1 has always been very active. Ds 1 has also been aggresive in the past but only like pushing other kids.  He started a program through the state (on thursdays) and all of a sudden this aggresive behaviour started. First he was fighting with another kid at his day program and bit him. Then later I was told that he was the instigator as far as hitting went at the program. He really didnt have any problems at home at this point. Then about 3 weeks ago, he started being mean to Ds 2, pushing him over for no reason and hitting him. I started watching two children during the day and it got alittle worse. Then I started a behavior chart and chore chart with smily faces and sad faces. It started to work. But then today I had a friend come over and she brought along her 4 yr old and 1 yr old. Her 4 yr old and Ds 1 started playing and it was fine at first but then he started being mean to him(ie pushing, hitting). Then he started pushing the 1 yr old. He s just being a bully. I have tried time outs, the behaviour chart, spanking (which I hate and hasnt worked in the past.) What can I do? I try to follow AP as much as possible but Im losing all patience with him. I am just at a loss. Plz help. I m at my wits end