1999 Gt No Start

The roads were clear and salt free last week so I decided to wake up my 1999 GT for a ride. The fuel pump would not prime so I applied power directly to it through the rear connecter (as I have done for the past few start-ups after long periods of storage). The pump ran and I got pressure at the rail. Upon turning on the ignition I got a really weird result- the speedo and tach pegged, the theft light flashed, the cooling fan went on- all for a few seconds then the dash went back to normal. Upon cranking, the fully charge battery had a major discarge and of course no start. Is this a major ECM failure?

Thanks for the quick reply. The battery was fully charged and cranked the engine normally when I first tried to start it. I have had it on trickle. After priming the pump with direct power, when I reconnected the harness and turned on the ignition I got the wierd reaction and battery drain. I disconnected the battery and put it back on charge. When the temps in the garage get a little higher (15 degrees now) I'll reconnect the battery and try again.