Who killed Alan Ervin in the Chrysalids?

In "The Chrysalids" by John Wyndham, Alan Ervin is killed by the Sealanders during their conflict with the inhabitants of Waknuk. His death occurs when he is captured while trying to escape with other telepaths. The Sealanders see him as a threat due to his association with the telepaths and their progressive views. This act illustrates the broader themes of fear and intolerance present in the novel.