Lehman Brothers and Bear Stearns collapsed in March, 2008, fifteen years ago.
On Monday, March 10, 2008, many of Bear's trading partners decided to stop trading with the bank.12 That put Bear in a bind, as it had only $18 billion in cash reserves.11
On March 11, 2008, Moody's downgraded Bear's MBS to B and C levels.10 The two events triggered an old-fashioned bank run, and its clients pulled out their deposits and investments.
By March 13, Bear Stearns' only had $2 billion left in cash.13 How did that happen so quickly? Bear hemorrhaged cash when the other banks called in their repurchase agreements and refused to lend more. No one wanted to get stuck with the Bear's junk securities. Source
This is looking like a take down to me.