Campus safety crises dominated headlines this week as law-enforcement searches extended into a fifth day following the Brown University classroom shooting and authorities pursued leads in a still-unidentified suspect. The university released new surveillance footage as investigators sought to reconstruct the attack and reassure students and families. Separately, MIT confirmed the killing of Nuno Loureiro, a 47-year-old plasma-physics and fusion researcher found shot at his Brookline home. Loureiro led MIT’s Plasma Science and Fusion Center and his death triggered a homicide investigation; university leaders called his killing a ‘‘shocking loss’’ and urged community solidarity. The twin incidents have intensified calls for upgraded campus threat-assessment protocols, improved coordination with local police, and additional mental-health response resources. University presidents and public-safety directors told reporters they will review readiness and communications plans as students return from breaks.