My understanding is this isn't a "run on the bank" situation, they were too successful growing their deposit book and couldn't grow their loan assets fast enough to keep pace. So they bought a lot of MBS so they at least were earning some yield with which to pay interest on their deposit liabilities but took heavy losses when rates moved against them so were inadequately capitalised. They tried to raise additional capital and a couple of key miscommunications in that process really spooked the market and they suddenly collapsed.