Who killed the cockroach?

11:30am Sunday Maria (my roommate) sends me a text message "Anna, are you awake? There is a giant cockroack smashed on the floor". She is right, there is a 6cm winged red cockroach smashed in our bathroom floor. I clean it and the animal's juices are stuck on the floor, who killed it did a great job. The strange thing is that we were the only ones in the appartment, so... WHO KILLED THE COCKROACH?

This is how the events went:
10:30pm Saturday, Maria leaves the appartment for a bbq while I am in the bathroom fixing my hair. No cockroach has been seen so far.
10:45pm Saturday, Mike leaves the appartment for a party while I am in my room getting dressed. He doesn't enter to the bathroom.
11:15pm Saturday, I leave the appartment after spending the last 30 min in the bathroom. No cockroach has been seen.
3:15am Sunday, I am the first one to get home. I go to the bathroom and I do not see any cockroach
3:30am Sunday, Maria gets home. Goes to the bathroom. No cockroach yet.
9am Sunday, I go to the bathroom wearing sandals, I am really sleep. I do not see any cockroach.
11:30am Sunday, Maria goes to the bathroom and sees the smashed cockroach on the floor.

None of our shoes had any evidence.
Other people with keys: Gerard (the neighbour with a sleepwalking disorder), Aleix (a friend who likes to get drunk, flirt and dance, lives about 15min far), Solange (cleaning lady), Mike (roommate that got home at 4pm on Sunday and swears that the last time he was home was saturday at 10:45pm).

WHO DO YOU THINK KILLED THE COCKROACH?