What was the rank of the roman soldier who stabbed Jesus while he was being crucified? Why would he stab Jesus? I read online that the roman soldier was sometimes referred to as a centurion. If that is the case, why would a senior roman officer partake in the execution of a lowly peasant? Wouldn't this duty be handled by lower-ranking legionaries?

Secondly, iirc, isn't it unusual for Romans to stab crucified victims with their spears since it wasn't listed in their doctrine? What would merit them to partake in this unorthodox behaviour?