diff --git a/.flowconfig b/.flowconfig
index 8a7e861c5c..28625456dc 100644
--- a/.flowconfig
+++ b/.flowconfig
@@ -12,7 +12,7 @@
 .*/node_modules/react-tools/src/vendor/core/ExecutionEnvironment.js
 .*/node_modules/react-tools/src/browser/.*
 .*/node_modules/react-tools/src/core/ReactInstanceHandles.js
-.*/node_modules/react-tools/src/event/.*
+.*/node_modules/react-tools/src/event/EventPropagators.js
 
 # Ignore jest
 .*/react-native/node_modules/jest-cli/.*
diff --git a/Libraries/ReactIOS/ReactIOSEventEmitter.js b/Libraries/ReactIOS/ReactIOSEventEmitter.js
index fa4afae61e..017a0fb0a4 100644
--- a/Libraries/ReactIOS/ReactIOSEventEmitter.js
+++ b/Libraries/ReactIOS/ReactIOSEventEmitter.js
@@ -7,7 +7,7 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule ReactIOSEventEmitter
- * @typechecks static-only
+ * @flow
  */
 
 "use strict";
@@ -57,21 +57,27 @@ var touchSubsequence = function(touches, indices) {
  * @param {Array<number>} indices Indices to remove from `touches`.
  * @return {Array<Touch>} Subsequence of removed touch objects.
  */
-var removeTouchesAtIndices = function(touches, indices) {
+var removeTouchesAtIndices = function(
+  touches: Array<Object>,
+  indices: Array<number>
+): Array<Object> {
   var rippedOut = [];
+  // use an unsafe downcast to alias to nullable elements,
+  // so we can delete and then compact.
+  var temp: Array<?Object> = (touches: Array<any>);
   for (var i = 0; i < indices.length; i++) {
     var index = indices[i];
     rippedOut.push(touches[index]);
-    touches[index] = null;
+    temp[index] = null;
   }
   var fillAt = 0;
-  for (var j = 0; j < touches.length; j++) {
-    var cur = touches[j];
+  for (var j = 0; j < temp.length; j++) {
+    var cur = temp[j];
     if (cur !== null) {
-      touches[fillAt++] = cur;
+      temp[fillAt++] = cur;
     }
   }
-  touches.length = fillAt;
+  temp.length = fillAt;
   return rippedOut;
 };
 
@@ -106,7 +112,11 @@ var ReactIOSEventEmitter = merge(ReactEventEmitterMixin, {
    * @param {TopLevelType} topLevelType Top level type of event.
    * @param {object} nativeEventParam Object passed from native.
    */
-  _receiveRootNodeIDEvent: function(rootNodeID, topLevelType, nativeEventParam) {
+  _receiveRootNodeIDEvent: function(
+    rootNodeID: ?string,
+    topLevelType: string,
+    nativeEventParam: Object
+  ) {
     var nativeEvent = nativeEventParam || EMPTY_NATIVE_EVENT;
     ReactIOSEventEmitter.handleTopLevel(
       topLevelType,
@@ -123,7 +133,11 @@ var ReactIOSEventEmitter = merge(ReactEventEmitterMixin, {
    * @param {TopLevelType} topLevelType Top level type of event.
    * @param {object} nativeEventParam Object passed from native.
    */
-  receiveEvent: function(tag, topLevelType, nativeEventParam) {
+  receiveEvent: function(
+    tag: number,
+    topLevelType: string,
+    nativeEventParam: Object
+  ) {
     var rootNodeID = ReactIOSTagHandles.tagToRootNodeID[tag];
     ReactIOSEventEmitter._receiveRootNodeIDEvent(
       rootNodeID,
@@ -156,7 +170,11 @@ var ReactIOSEventEmitter = merge(ReactEventEmitterMixin, {
    * Web desktop polyfills only need to construct a fake touch event with
    * identifier 0, also abandoning traditional click handlers.
    */
-  receiveTouches: function(eventTopLevelType, touches, changedIndices) {
+  receiveTouches: function(
+    eventTopLevelType: string,
+    touches: Array<Object>,
+    changedIndices: Array<number>
+  ) {
     var changedTouches =
       eventTopLevelType === topLevelTypes.topTouchEnd ||
       eventTopLevelType === topLevelTypes.topTouchCancel ?