I am not a bug expert, its the reason I didn't post earlier but It does not look like a cannabis predator. A number of pests has been recorded to be bad for mj but that bug in your pic is not one of them.
This is not a beetle , it belongs to the order Hemiptera , or true bugs . This can be determined by the the 1st set of wings ( half hard - half membraneous ) also it will have a sucking beak for a mouth. Beetles have the 1st set of wings all hard and have chewing mouth parts . There are both predatory hemiptera and there are others that suck the juices from plants . This is one of the juice suckers , commonly known in my area as a boxelder bug. One single one cannot do much , but when they appear in masses they can cause damage . You were right to eliminate it .