A goal down in two minutes to Brett Pitman and reduced to 10 men three minutes later it proved a nightmare for Birmingham’s caretaker boss Malcolm Crosby.
They could do nothing right and Bournemouth capitalised on the situation to add two further first half goals through Callum Wilson and Matt Ritchie.
Marc Pugh added the fourth, fifth and seventh goals after the break with substitute Tokelo Rantie converting an 80th minute penalty. Rantie completed Birmingham’s humiliation with the eighth goal four minutes from time.
Following such a dire start there was little chance of Birmingham staging a revival as Bournemouth were generally in control and went on to record their sixth win in their last seven outings.
These are bleak times for Birmingham, highlighted by the sacking of manager Lee Clarke on Monday.
During his stewardship Birmingham had won only one of their previous 24 homes games and this latest heavy defeat keeps them anchored in the relegation area and facing a bleak future.
In their hour of crisis the West Midland’s club could not have made a worse start. They were caught in total disarray when Pitman simply ran through unchallenged to slip the ball past the advancing Darren Randolph.
Things became even worse in the fifth minute. There was no real danger when Wilson attempted to gain possession only to be pulled back by Edgar who was immediately shown a red card by referee Keith Hill.
Against 10 men, Bournemouth had a fine opportunity to completely destroy a hapless Birmingham but their early marksman, Pitman, suddenly lacked his finishing touch.
Twice in quick succession he should have added to his tally. On the first occasion Randolph bravely pushed out an effort from Wilson only for Pitman to glide his effort wide.
A minute later he completely mis-screwed his shot wide with the goal at his mercy but Wilson made no mistake with his 35th minute goal.
Yet again it came about as a result of a mistake. This time Randolph made a woeful clearance straight to the Cherries striker. He calmly went forward, rounded Randolph and scored with a low angled shot for his tenth goal of the season.
The chronicle of errors continued unabated as Bournemouth notched a third goal six minutes before half time.
Randolph came out only to see Paul Robinson’s clearance bounce back off Ritchie who then ran gleefully on to the loose ball to score into an empty net.
Birmingham could do nothing right as they even missed a 53rd minute penalty. Clayton Donaldson was impeded by Tommy Elphick but Paul Caddis saw Artur Boruc save his spot kick low down diving to his left.
There was no respite for Birmingham as Pugh hooked home a right wing cross from Simon Francis in the 64th minute.
Pugh headed home Bournemouth’s fifth in the 70th minute when he converted another accurate Francis cross.
Rantie notched an 80th a penalty followed by another Pugh goal. Rantie completed the demolition of demoralised Birmingham four minutes from time.