This is only my thoight od why Sergio is where hes at,at this point.
I think Sergio wants the boys to move on and get on with their lives, like it was before, baseball games, ETC, the boys are grieving severely for their sister and it pizzez him off.
He needs to be the actor at all times, the boys went back to school and mentioned what was going on, especially the youngest, Sergio got wind of it and voluntarily expressed his feelings to either Becky or the police, of something like, " I (sergio) feel so much stress from all this, Im very edgy, on & on & on, I feel as though Im not doing the boys any good, then ,the famous line, "I need some space".
In other words, He's the center of attraction(actor) yet he feels its for a good reaSon, next thing weLL know ,he will turn himself into a psych ward, remember the case with celina ? and the step dad? Thats what Im seeing, JMO,JMO,JMO