Integration of Lambda, api gateway and event bridge where Target is set as sns topic for 5xx error.

I want to get the 5xx error of api gateway REST api which has to be integrated with event bridge to set the rule regarding the event pattern for aws.apigateway. However I have given iam role to lambda and inside the lambda trigger is api gateway, code for lambda is to generate the status code 503, which is here used to forcefully create the error of 5xx.